Considering the time and money you'll invest in a new mattress, it pays to do your homework. You can find good descriptions of mattress types and advice on how to test a mattress at bettersleep.org, run by the industry-funded Better Sleep Council.

TEST BEFORE YOU BUY

The “best” mattress comes down to personal preference — consumers are urged to test mattresses before buying. It also pays to know what’s inside each type — and why. Here’s a look at different mattresses.

InnerspringThe top seller in mattresses, an innerspring uses tempered steel coils as support. The number, type and configuration of coils vary by product. Layers of upholstery — foam and fabric — provide insulation and cushioning.Example: Sealy, Simmons and Serta are the best-known brands.Advantage: Traditional, most widely available.Drawback: Inexpensive models can sag after a few years of use.

FoamFoam mattresses can be made with solid cores or of layers of different types of foam laminated together. Materials include refinements to traditional latex, polyurethane, and viscoelastic (memory) foam, which mold to the user’s form.Example: Tempur-pedic beds (viscoelastic foam).Advantage: Viscoelastic is considered highly durable.Drawback: Cold weather can make some foams feel less firm.

AirbedsAir-filled core provides support and can be designed to look like a familiar mattress/box spring combination. Sections are usually adjustable to users’ preferences.Example: Sleep Number.Advantage: Partners can choose own comfort levels.Drawback: Some say some air mattresses not firm enough.

AdjustableElectrically adjustable beds allow users to position the bed’s head and foot as desired. Mattresses can be innerspring, foam or a combination, but must be built for flexing.Example: Craftmatic Adjustable.Advantage: Beneficial for people with health problems.Drawback: Some beds can prevent movement during sleep.

FutonsUsually a flexible combination of foam, cotton and synthetic fibers.Advantage: Can be converted from bed to sofa.Drawback: Usually not as comfortable as conventional mattresses.

WaterbedsWater-filled core with upholstery for insulation and comfort. Advantage: Easily cleaned to help prevent allergies; can be heated.Drawback: Not easily moved.

Many people are tossing and turning on potentially bad beds because they dread mattress shopping.

About half of 252 members of USA TODAY's shopper panel responding to an informal survey said mattress shopping is intimidating. Maybe that's why a third are sleeping on mattresses that are at least 8 years old, while mattress makers and sellers suggest getting a new mattress every five to seven years.

Part of the problem is that comparison shopping is difficult. It's nearly impossible to find a model with the same name at different retailers.

Then there's the cost. You'll spend at least $600 for a good-quality mattress and close to $1,000 for a really good one. Premium models are several thousand dollars.

Consumer Reports magazine, known for its picks of best and worst models of products ranging from cars to vacuum cleaners, says no brand, model or type of mattress is clearly superior to another. It depends on how it feels to you. The magazine doesn't rate mattresses because its own testers disagree so vigorously over what mattresses are best.

Because of that, you should never buy a mattress without a test drive. Ask friends and colleagues to recommend mattress retailers where they found good service, prices and products. Or visit a few stores to get a feel for the different sales approaches and mattresses. And remember, as with buying a car, you can always walk away.

Don't base your decision just on cost, says Nancy Shark, spokeswoman for the industry-funded Better Sleep Council. Consider all the services a store offers, including whether it will pick up your old mattress when it delivers a new one.

And don't be shy about testing out the mattress, she says. "People might feel uneasy about lying down on a bed in a public place. But retailers expect you to do that. You need to do that."

Below is advice from experts to help you navigate the mattress-buying process.

Contributing: Priyanka Dayal, Barbara Hansen

5 things you need to know before you shop for a mattress

1. You may not need a new mattress.

Even though a mattress is past the industry-recommended five to seven years for replacement, it may be just fine. If the mattress was a particularly high-quality one, is not used — or abused — often, it could have a few more good years in it.

But if there's a crater in the middle or the stuffing is coming through the seams, start shopping.

Other signs it might be new-mattress time:

•You're waking up with unexplained aches and pains.

•You're not sleeping as well as you once did in your bed.

•You sleep much better in hotels or at other people's homes.

2. Even if you need a new mattress, you may not need a new box spring.

During Consumer Reports' research on mattresses, testers realized that box springs often don't actually have springs but are more like "wire structures," says Ed Kippel, who managed the project. He suggests keeping a box spring unless it has major indentations or is ripped or otherwise damaged.

John O'Connell, senior vice president of merchandising at 1-800-Mattress, acknowledges that it's "not mandatory" to change the box spring. Still, O'Connell says, an older box spring or "foundation" might not have the correct support for a new mattress. And he warns that sagging in a box spring is rarely noticeable.

Another consideration: If you mix and match a mattress and box spring, you might void or reduce warranty coverage. The retailer could say your mattress is sagging because it was on an old or incorrect box spring.

3. Don't buy based on the warranty.

Mattress warranty offers often sound too good to be true and, at a minimum, they are often at least unrealistic. After all, the industry says you should get a new mattress after seven years. But some warranties last 20 years or more, although they often are prorated, except for premium mattresses.

Warranties don't cover normal wear from use, but rather manufacturers' defects such as springs breaking or protruding through the mattress or sag. O'Connell says more than 1½ inches of sag is considered a defect.

He also notes that manufacturers' warranties are void and mattresses can't be returned if they are stained, soiled or abused.

Michael Zippelli, CEO of high-end mattress maker and retailer Dormia, says retailers know few people return mattresses after the first few years. "Warranties are inflated in our industry," he says. "Retailers use it to try to one-up competition."

4. You can negotiate.

Don't decide you can't afford a mattress simply because the posted or "as delivered" price is too high. Lisa Lee Freeman, editor in chief of Consumer Reports' ShopSmart magazine, suggests asking the salesperson: "Can you do something for me?" The salesperson might drop the delivery fee or offer a better deal if you suggest, for example, that you are considering a cheaper similar model by the same manufacturer at another store.

"Pricing in mattresses is all over the place," Freeman says. "And they're constantly on sale. We found the exact same model one day was $1,300, and the next day, it was $2,600."

Because retailers do ask manufacturers to design mattresses to different specifications — and then give them different names — negotiating can be difficult.

Zippelli, whose mattresses are sold in retailers including Sleepy's and Mattress Discounters and in 20 of his own stores, says that if customers see the same product by the same manufacturer at competing retailers, "price matching is not uncommon" and is Dormia's policy. Some retailers even extend the offer after a mattress is delivered.

But how to define the "same product"?

Zippelli suggests comparing the density of the foam and the number of layers. Ask the retailer the weight per square foot of the foam. The range is typically 1 pound to 7 pounds per cubic foot. For mattresses that also have coils, you should also ask about the number of coils for further comparison.

Your comfort should determine how much foam or how many coils are appropriate.

5. Safety matters, which is why you may want to wait until after July 1 to buy.

It might pay to wait a few months if you are due for a new mattress. Starting July 1, all new mattresses must meet a tough new fire-resistance regulation.

While most national mattress retailers were already meeting a new California flammability standard, industry officials say the new federal standard is more stringent.

Mattresses that meet the standard — and many already do — will have a federal label indicating they are in compliance.

Nancy Nord, acting chairman of the Consumer Product Safety Commission, says that after July 1, new mattresses will be designed to be more resistant to fires from candles or other open flames.

That will give people more time to "discover a fire and get out of the house," she says.

To report corrections and clarifications, contact Reader Editor Brent Jones. For publication consideration in the newspaper, send comments to letters@usatoday.com. Include name, phone number, city and state for verification.

Joel and Elizabeth Perea try out a bed at American Furniture Warehouse in Englewood, Colo.

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